Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of X-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in ...Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of X-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in sub-micron-width silicon trenches with an aspect ratio greater than 35 over a grating area of several square centimeters is challenging and has not been described in the literature previously. A comparison of pulsed plating and constant current plating led to a gold electroplating protocol that reliably filled trenches for such structures.展开更多
This study shows a silver electrodeposition model (EDM) on a graphite substrate. The electrolyte was a 0.01 M solution of pure silver and chromium nitrate using an electrolyzing cell. EDC with current density up to 20...This study shows a silver electrodeposition model (EDM) on a graphite substrate. The electrolyte was a 0.01 M solution of pure silver and chromium nitrate using an electrolyzing cell. EDC with current density up to 20 mA/cm<sup>2</sup> and 15 mV and pulse current were studied. Results revealed that silver deposited at a rate of 0.515 mg/cm<sup>2</sup>/min with 12 mA/cm<sup>2</sup> that decreases to 0.21 and 0.16 mg/cm<sup>2</sup>·min with the decrease of current density to 6 and 5 mA/cm<sup>2</sup> respectively. The model postulates that silver ions (a) were first hydrated before diffusing (b) from the solution bulk to the cathode vicinity, The next step (c) involved the chemical adsorption of these ions on certain accessible sites of the graphite substrate (anode), The discharged entities (d) adhere to the graphite surface by Van der Vales force. Silver ions are deposited because the discharge potential of silver is low (0.38 mV) as compared to other metal ions like chromium (0.82 mV). Pulse current controls silver deposition due to flexibility in controlling steps (a)-(c) of the deposition mechanisms. Parameters like current density, current on-time, current-off time, duty cycle (ratio of current on time and total pulse time) and pulse frequency influenced the shape and size of the deposits. Step (b) suggested that silver particles were deposited in a monolayer thickness. The silver layer turned multiple after fully satisfying the accessible sites with the monolayer. The activation energy ΔE value amounts to 86.32 kJ/mol/K. At high temperature and current density, homogeneous diffusion occurs.展开更多
Tungsten coating is considered as a promising alternative material for plasma facing materials(PFC) in future fusion devices.The electro-deposition of tungsten in Na_2WO_4-ZnO-WO_3 melt at 1173 K on low activation ste...Tungsten coating is considered as a promising alternative material for plasma facing materials(PFC) in future fusion devices.The electro-deposition of tungsten in Na_2WO_4-ZnO-WO_3 melt at 1173 K on low activation steel substrates was studied in this work.Adherent and smooth tungsten films were deposited under various pulsed current conditions.The crystal structure and microstructure of tungsten deposits were characterized by XRD,SEM and EDX techniques.The results show that pulsed current density and duty cycle have a significant influence on tungsten nucleation and electro-crystallization phenomena.Uniform and smooth tungsten coating with high purity and high adherence is obtained on low active steel substrates as cathodic current density ranges from 35 to 25 mA·cm_(-2).展开更多
In recent research, a novel method combined with pulse current （PC） deposition and the ultrasonic （U） field was used to fabricate pure nickel and nickel-ceria composite coatings, respectively. Morphology, crack pr...In recent research, a novel method combined with pulse current （PC） deposition and the ultrasonic （U） field was used to fabricate pure nickel and nickel-ceria composite coatings, respectively. Morphology, crack propagation, and crystal texture were observed and analysed by using environment scanning electron microscopy （E-SEM） and transmission electron microscopy （TEM）. Orthogonal experiment [L16 （45）] was designed to optimize the parameters of pulsed power and the appropriate amount of RE addition based on microhardness. Effect of RE addition and pulsed current on the mechanism of co-electrodeposition was also investigated and compared. Experimental results indicated that it produced the alloying coatings, exhibiting compact grain and amorphous state. Nano-sized RE would preferentially occupy and pad at the edge of cracked gaps and micropore to limit the growing location and space for coarse Ni grain. Furthermore, during annealing at 480 ℃ for 2 h, a solid-solution precipitated phase named NiCexO1-x （0展开更多
文摘Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of X-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in sub-micron-width silicon trenches with an aspect ratio greater than 35 over a grating area of several square centimeters is challenging and has not been described in the literature previously. A comparison of pulsed plating and constant current plating led to a gold electroplating protocol that reliably filled trenches for such structures.
文摘This study shows a silver electrodeposition model (EDM) on a graphite substrate. The electrolyte was a 0.01 M solution of pure silver and chromium nitrate using an electrolyzing cell. EDC with current density up to 20 mA/cm<sup>2</sup> and 15 mV and pulse current were studied. Results revealed that silver deposited at a rate of 0.515 mg/cm<sup>2</sup>/min with 12 mA/cm<sup>2</sup> that decreases to 0.21 and 0.16 mg/cm<sup>2</sup>·min with the decrease of current density to 6 and 5 mA/cm<sup>2</sup> respectively. The model postulates that silver ions (a) were first hydrated before diffusing (b) from the solution bulk to the cathode vicinity, The next step (c) involved the chemical adsorption of these ions on certain accessible sites of the graphite substrate (anode), The discharged entities (d) adhere to the graphite surface by Van der Vales force. Silver ions are deposited because the discharge potential of silver is low (0.38 mV) as compared to other metal ions like chromium (0.82 mV). Pulse current controls silver deposition due to flexibility in controlling steps (a)-(c) of the deposition mechanisms. Parameters like current density, current on-time, current-off time, duty cycle (ratio of current on time and total pulse time) and pulse frequency influenced the shape and size of the deposits. Step (b) suggested that silver particles were deposited in a monolayer thickness. The silver layer turned multiple after fully satisfying the accessible sites with the monolayer. The activation energy ΔE value amounts to 86.32 kJ/mol/K. At high temperature and current density, homogeneous diffusion occurs.
基金supported by the International Thermonuclear Experimental Reactor (ITER) Project of China (No. 2010GB109000)the National Natural Science Foundation of China (No. 50972008)
文摘Tungsten coating is considered as a promising alternative material for plasma facing materials(PFC) in future fusion devices.The electro-deposition of tungsten in Na_2WO_4-ZnO-WO_3 melt at 1173 K on low activation steel substrates was studied in this work.Adherent and smooth tungsten films were deposited under various pulsed current conditions.The crystal structure and microstructure of tungsten deposits were characterized by XRD,SEM and EDX techniques.The results show that pulsed current density and duty cycle have a significant influence on tungsten nucleation and electro-crystallization phenomena.Uniform and smooth tungsten coating with high purity and high adherence is obtained on low active steel substrates as cathodic current density ranges from 35 to 25 mA·cm_(-2).
基金Project supported by National Natural Science Foundation of China (50775113)Natural Science Foundation of Jiangsu Province (BK2007201)
文摘In recent research, a novel method combined with pulse current （PC） deposition and the ultrasonic （U） field was used to fabricate pure nickel and nickel-ceria composite coatings, respectively. Morphology, crack propagation, and crystal texture were observed and analysed by using environment scanning electron microscopy （E-SEM） and transmission electron microscopy （TEM）. Orthogonal experiment [L16 （45）] was designed to optimize the parameters of pulsed power and the appropriate amount of RE addition based on microhardness. Effect of RE addition and pulsed current on the mechanism of co-electrodeposition was also investigated and compared. Experimental results indicated that it produced the alloying coatings, exhibiting compact grain and amorphous state. Nano-sized RE would preferentially occupy and pad at the edge of cracked gaps and micropore to limit the growing location and space for coarse Ni grain. Furthermore, during annealing at 480 ℃ for 2 h, a solid-solution precipitated phase named NiCexO1-x （0
